MMP1 and atrial fibrillation: To investigate the expression pattern of the inflammatory mediators and catabolic enzymes in human AF and NP cells treated with IL-1β stimulation, the gene and protein expressions of IL-6, IL-8, the VEGF family, MMP-1, and MMP-3 were measured in IL-1β-stimulated human AF or NP cells by qRT-PCR and ELISA.